The invention relates to a miniaturized x-ray source situated in a catheter that generates x-rays while minimizing risk of exposure to the x-rays.
Traditionally, x-rays have been used in the medical industry to view bone, tissue and teeth. X-rays have also been used to treat cancerous and precancerous conditions by exposing a patient to x-rays using an external x-ray source. Treatment of cancer with x-rays presents many well documented side effects, many of which are due to the broad exposure of the patient to the therapeutic x-rays.
Minimally invasive endoscopic techniques have been developed and are used to treat a variety of conditions. Endoluminal procedures are procedures performed with an endoscope, a tubular device into the lumen of which may be inserted a variety of rigid or flexible tools to treat or diagnose a patient""s condition.
The desire for improved minimally invasive medical devices and techniques have led to the development of miniaturized x-ray devices that may be used in the treatment or prevention of a variety of medical conditions. International Publication No. WO 98/48899 discloses a miniature x-ray unit having an anode and cathode separated by a vacuum gap positioned inside a metal housing. The anode includes abase portion and a projecting portion. The x-ray unit is insulated and connected to a coaxial cable which, in turn, is connected to the power source. An x-ray window surrounds the projecting portion of the anode and the cathode so that the x-rays can exit the unit. The x-ray unit is sized for intra-vascular insertion, and may be used, inter alia, in vascular brachytherapy of coronary arteries, particularly after balloon angioplasty.
International Publication No. WO 97/07740 discloses an x-ray catheter having a catheter shaft with an x-ray unit attached to the distal end of the catheter shaft. The x-ray unit comprises an anode and a cathode coupled to an insulator to define a vacuum chamber. The x-ray unit is coupled to a voltage source via a coaxial cable. The x-ray unit can have a diameter of less than 4 mm and a length of less than about 15 mm, and can be used in conjunction with coronary angioplasty to prevent restenosis.
U.S. Pat. No. 5,084,061 discloses an intragastric balloon with improved valve locating means. The balloon has an ellipsoid or like configuration so that the balloon implanted in the stomach tends to rotate or rock only about one axis when a surgeon attempts to manipulate the balloon, for example, for the purpose of finding a filler valve and inserting a filler tube into it. For easy location, the filler valve is disposed on the equator. A retrieval tab is mounted to the exterior of the balloon, to permit capturing of the balloon and retrieval from the stomach, after the balloon has been deflated and is no longer desired for weight control purposes. Visual and x-ray opaque markers are located in the proximity of the valve and of the retrieval tab to facilitate their visualization with an endoscopic light when the balloon is in the stomach.
U.S. Pat. No. 5,127,394 describes a fluoroscopy-switching device and method for preventing accidental over radiation of a patient in surgical procedures involving both fluoroscopy and endoscopy. Video outputs from the endoscope and fluoroscope is connected to a switching device. The endoscope generates a video signal having a first video format, and the fluoroscope generates a video signal having a second video format. The physician uses the switching device to select from between the endoscope video output and the fluoroscope video output for viewing on a video monitor which accepts a video signal of a predetermined video format. The switching device is operable to convert at least one of the endoscope video signal or the fluoroscope video signal to the predetermined video format, which the monitor accepts. When the endoscope video output is selected for viewing, the switching device automatically deactivates the x-ray generator of the fluoroscope. When the switching device is actuated to select the fluoroscope video signal for viewing on the monitor, the switching device automatically reactivates the x-ray generator. In this manner, over radiation of the patient during periods when the fluoroscope is not being used.
U.S. Pat. No. 4,993,404 describes a fluoroscopy-switching device for preventing accidental over radiation of a patient in surgical procedures involving both fluoroscopy and endoscopy. Video outputs from the fluoroscope and endoscope is connected to a switching device. The physician uses the switching device to select from between the endoscope video output and the fluoroscope video output for viewing on a video monitor. When the endoscope video output is selected for viewing, the switching device automatically deactivates the x-ray generator of the fluoroscope. When the switching device is actuated to select the fluoroscope video signal for viewing on the monitor, the switching device automatically reactivates the x-ray generator. In this manner, over radiation of the patient during periods when the fluoroscope is not being used is avoided.
Miniaturized x-rays are not foolproof, however, and still present difficulties. The x-ray unit generates heat, which can damage adjacent tissue. Additionally, x-rays are not localized and irradiate local tissue rather than only irradiating the desired site. Also, it is difficult to maintain the positioning of these instruments inside at the desired location. Improved miniaturized x-ray units the overcome these difficulties are desirable.
Other techniques are used to treat tumors with x-rays, including planting a seed of radioactive material at the tumor site, typically accomplished with endoluminal procedures. However, the patient becomes xe2x80x9chotxe2x80x9d, i.e., radioactive, and the procedure risks exposure of the medical personnel to radiation exposure.
As noted above, many types of cancerous and precancerous conditions are treated by irradiating the tumor or site with x-rays. However, the x-rays are broadcast over a large area of healthy tissue in addition to the tumor, since the radiation is administered from outside the body so that it penetrates the skin and any internal organs or tissue to reach the desired site. To avoid this, miniaturized x-ray systems which generate x-rays at the desired site are a desirable alternative to conventional apparatus.
Many types of cancer occur in a body cavity or lumen, such as in the rectum, vagina, esophagus or pulmonary passages. It would be desirable to treat these cancers using miniaturized x-ray sources in combination with endoscopic techniques, which are minimally invasive to the patient, so that the cancer or other intraluminal tissue is directly treated with x-rays. This technique would minimize exposure of health tissues to the x-rays.
One problem with such devices and techniques is proper placement of the x-ray source is correct within the lumen. This problem leads to the additional concern of how to insure the delivery of the correct dose of the x-ray source. Providing an electronically controlled x-ray source into a lumen would require a precise means for determining the placement as well as the dose of the x-ray. What is required is a solution to this problem.
Another problem is with use of x-rays to kill lesions that are located behind the surface of healthy tissue regions in the body. This may require killing healthy tissue since the healthy tissue is also exposed to the x-rays.
Another difficulty arises between x-ray dose and thickness of the target tissue or tumor. With thicker lesions, the x-ray source has to be larger and more powerful to penetrate the tissue. However, as the x-ray dose is increased, so is the size of the device and its associated power and heating concerns.
The present invention overcomes the difficulties associated with x-ray therapy and apparatus of the prior art by providing an endoscopic x-ray device that generates x-rays at the site of treatment and minimizes exposure of other tissues to irradiation.
The present invention relates to an x-ray device having a tapered or pointed tip having an x-ray source therein. The x-ray device can penetrate into tissue inside a body lumen to deliver x-rays to the target tissue while minimizing irradiation of surrounding tissue. The device is described in more detail below, with reference to the accompanying drawings which illustrate preferred embodiments of the invention.